Gaseous electric discharge apparatus



July 21, 19 H. w. LQ'RD ETAL 2.290.693 GASEOUS ELECTRIC DISCHARGE APPARATUS Eiled Kw. 16, 1939 Inventors: Harold W.Lor-d Martin A. Edwards, by flm ycfiflm.

Their Attofney.

Patented July 21.1942

UNITED f STATE GASEOUS ELECTRIODISCHARGE APPARATUS Harold w. Lord and- Martin'A. Edwards, Schenectady, N. Y-., assignor to General Electric Company, a corporation of New York Application November 16, 1939, Serial No. 304,755- 8 Claims. (Q1. 176-124) Our invention relates to gaseous electric discharge devices, such as discharge lamps, and apparatus for. operating them from alternating current circuits. It relates particularly to discharge devices which have electrodes that are initially heated to an electron emitting temperature and to apparatus which, when the electrodes have reached that temperature, applies the starting voltage to the device. It is the object of our invention to provide apparatus of this character which will produce rapid and ample initial heating of the electrodes, which will have low losses after the starting and during the normal operation of the device and which will eliminate any reset time.

Our invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. i

In the single 'figure of the drawing which is a circuit diagram illustrating one embodiment of our invention, the gas filled electric discharge device or lamp I having the initially heated thermionic electrodes 2 at the ends thereof is shown connected through the ballast reactor 3 and the control switch 6 with the source of alternating dition of resonance depends upon the saturation of the transformer and the latter depends upon and the primary may be termed a voltage sensithe transformer andin the heating circuit are.

current supply such for example as a 60 cycle,

115 volt lighting circuit.

Connected across the device I and in series with the electrodes 2 is the thermal switch 6 which, for example, may be abimetallic switch.

v Normally this switch is in open circuit position and preferably is enclosed in an evacuated envelope. For heating the switch to cause it to close we employ-the resistance heater I which may be of any well known form such as a coil of resistance wire. Current. is supplied to the heater 1 from the secondary 8 of the transformer.

9 which is constructed to have high leakage reactance of non-linear characteristics.

The transformer core as'shown has a center the voltage the circuit comprising the capacitor tive non-linear, resonant circuit. After thedischarge starts the arc drop voltage between the electrodes is insufiicient to maintain saturation in the leg II; hence the circuit goes out of resonance and as a result the current flow through the, primary of the transformer during the nor-e mal operation of the discharge device reduces to a very low value at which value the losses in negligibly small.

The operation of the apparatus will be readily apparent from the above description. When the apparatus is thrown upon the supply the closing of the switch t the device does not immediately'start since the line voltage is in sufiicient in itself to cause a breakdown between the electrodes thereof. Current does flow through thereac'tor 3, the two filaments 2, the capacitor 12 and the transformer primary. Since the leg ll saturates at the voltage'thus applied to the transformer the capacitor mary. The resulting current flow gives the electrodes a certain amount of heat and simultaneously causes current to be induced in the secondary 8 whereby the switch 6 is' rapidly heated by the heater I and warped into closed circuit position. The low impedance shunt circuit thus pro-.- vided causes the electrodesquickly to come to an leg wound with the primary Ill and two outer legs of which one is wound with the secondary 8. The other leg, indicated at H, becomes saturated when the voltageapplied to the primary reaches a predetermined value such as the value initially impressed upon it by theclosing ofthe switch 4 and before the discharge starts in the-- device I. The saturation'of the leg I I has a twofold efiect; it forces flux through the secondary to generate heating current and it reduces the inductive reactance of the primary. The caelectron emitting temperature. The closing of the switch 6, however,'short circuits the circuit of the transformer primary whereby current in the heating circuit is reduced substantiallyto' .zero. Upon cooling, the switch opens thereby producing a voltage impulse across the device which efiects the starting thereof and after the device has .once started the arc drop voltage across it is insufficient to maintain the transformer leg ll saturated and a condition of resonance in the circuit. By continuing to cool, the switch returns to an open circuit position which is substantially the same as that which is occupied before the switch 4 was closed, sincethe circuit, being no longer in resonance and the reactance of the primarybeing high, now supplies only a small amount of energy to the heater.

The switch 6 in this position is reset for a subsequent starting-operation, hence with apparapacitor l2 connected in series with the primary is constructed to resonate with the primary when it has its low reactance value. Since the contus of this. character any reset time is entirely eliminated. I

What we claim as new and desire to secure by Letters Patent of the United States is:

circuit by resonates with the pri- I 1'. In combination, a source of alternating current supply, an electric discharge device connected to -be supplied therefrom and havingelectrodes between which a discharge takes place v constructed to be initially heated to an electron rent supply, an electric discharge device connected to be supplied therefrom and having electrodes between which a discharge takes place constructed to .be initially heated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a resistance heater for said switch and a supply circuit for said heater connected to be responsive to the voltage across said device and including current controlling impedance means having a non-linear characteristic.

3. In combination, a source of alternating current supply, 'an electric discharge device connected to be supplied therefrom and having electrodes between which a discharge takes place constructed to be initially heated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a heater for saidswitch and means including a transformer having non-linear characteristics connected across said device for supplying heating current thereto.

4. In combination, a source of alternating cur rent supply, an electric discharge device'connected to be supplied therefrom and having electrodes between which a discharge takes place constructed to be initiallyheated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a resistance heater for said switch, and a high leakage reactance transformer' having non-linear characteristics, said transformer having its secondary connected to supply said heater and having its primary connected to be responsive to the voltage across said device.

5. In combination, a source of alternating current supply, an electric discharge deviceconnected to b e supplied therefromand having electrodesbetween which a'discharge' takes place constructed to be initially heated to an electron emitting temperature, a normally open thernfal switch cormected across the device in series with said electrodes, a resistance heater for said switch, and means for supplying heating current to said heater comprising a circuit connected in parallel with said switch adapted to resonate in response to the application of starting voltage thereto.

6. In combination, a source of alternating current supply, an electric discharge device connected to be supplied therefrom and having electrodes between which a discharge takes place constructed to be initially heated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a resistance heater for said switch, and means comprising a non-linear resonant circuit connected to be responsive to the voltage across said device for supplying heating current to said electrodes. I i 7. In combination, a source'of alternating current supply, an electric discharge device connected to be supplied therefrom and having electrodes between which a discharge takes place constructed to be initially heated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a resistance heater for said switch, and means for supplying heating current to said heater comprising a transformer having its secondary connected across said heater and having a leakage path constructed to saturate when the starting voltage of the device is applied to the transformer primary and to desaturate when the arc drop voltage of the device is applied thereto, a capacitor and means connecting the capacitor and the primary in a series-circuit across said device, said capacitor being constructed to resonate with'said primary in response to the saturation of said leakage path. 8. In combination, an electric discharge device arranged to be supplied from a source of alternating current and having electrodes between which a discharge takes place constructed to be initially heated to an electron emitting temperature, a normally open thermal switch connected across the device in series with said electrodes, a heater for actuating said switch. and means having a non-linear volt-ampere characteristic connected across said switch for energizing said heater.

HAROLD- W. LORD.

MAR'I'IN A. EDWARDS. r 

